Taenia Tapeworms

(Taenia spp.)

Tapeworms belonging to the genus Taenia are common in dogs that have access to raw meat. The primary significance of these canine tapeworms resides in their ability to infect livestock with larval forms that result in meat condemnation and economic loss at slaughter. A single canine species, Taenia multiceps is zoonotic.

Parasite: Taenia hydatigena, Taenia ovis, Taenia multiceps, Taenia pisiformis, Taenia serialis
Common name: Tapeworms
Host: Dogs, foxes, wild canids
Pre-patent period: 6-8 weeks
Location of adults: small intestine
Distribution: worldwide
Transmission route: ingestion of larval metacestode forms (cysticercus, coenurus) in intermediate host tissue (primarily livestock)
Zoonotic: No, except for T. multiplex.

Distribution

Worldwide.

Clinical signs

Tapeworms are rarely harmful to dogs and cats and most animals are asymptomatic. Heavy infections may cause non-specific abdominal symptoms such as diarrhoea or constipation and abdominal pain accompanied by ill-thrift, and a pot-bellied appearance.

Figure 1. Stained mature proglottid of Taenia pisiformis. (Image credit: M I (Spike) Walker / Alamy Stock Photo.)
Figure 2. Taeniid egg on faecal floatation. (Image credit: Dr Rebecca Traub.)

Diagnosis

Proglottids (tapeworm segments) may actively crawl in faeces or around the perianal area of animals (most commonly observed by the owner). Fresh proglottids may be relaxed in water and squashed between two glass slides for morphological examination. Proglottids contain uterine pores opening laterally (Fig 1). Gravid segments contain typical taeniid eggs (Fig 2). Faecal floatation is not recommended for diagnosis as Taeniid eggs are not actively shed in faeces. Eggs of Taenia spp. CAN NOT BE DISTINGUISHED from those of Echinococcus.

Treatment

Praziquantel given orally at 5 mg/kg is the drug of choice.

Control

Owners should be strongly encouraged not to feed their dog raw offal or meat of domestic or wild intermediate hosts (e.g. livestock, rabbits). In Taenia endemic areas, dogs should be treated with praziquantel at 6-weekly intervals.

Public health considerations

Ingestion of T. multiceps eggs passed in the faeces of canids may result in the larval stage of the tapeworm developing in the central nervous system, eye, subcutaneous or intramuscular tissue of humans, referred to as human coenurosis. Treatment is complicated and usually requires a combination of surgical and chemotherapeutic intervention.